Chemicals with distinct properties show different characteristics in transport and partitioning (or binding) into certain phases and produce different impacts. In biological systems, it is important to establish criteria on the effectiveness of chemicals to partition or bind to lipid tissues and cell membranes. Such information is fundamentally important to the elucidation of chemical toxicity and efficacy of detoxification by enzymes, and to the assessment of bioaccumulation potential in organisms. We propose to investigate the partition/binding characteristics of environmental toxicants (benzene derivatives, organochlorines and PCBs) from aqueous solution into a model lipid component (trioleins) and into a model cell-membrane component (egg lecithin) as in vitro standards of chemical affinities with these systems. We will attempt to identify, especially with the model membrane system, the effects resulting from the polarity, size, structure, and functional groups associated with toxicants and lipid and membrane systems. The influence of the ordered bilayer structure on binding will be or particular concern. The data from these systems will further be evaluated in comparison with the partition coefficients of the same compounds in the analysis, to determine the extent of correspondence and/or discrepancy between the respective lipid-water and octanol-water systems.